You're bundled against the Arctic chill. You're loaded with equipment. And that big white bear who's just slashed your tires has a toothache.

Where is that helicopter? Norbert Rosing leads young readers into the wintry world of the dangerous polar bear, who has good reason to be angry at man's intrusions.

Let this National Geographic expert show you the bears' playful side; learn how they make nests for hibernation, why their coats are so white, and how you can help to protect their environment from the effects of global warming.